One of such a carrier apparatus for carrying goods is a suitcase that has one or more power assisted wheels. For example, JP2001-87024A discloses this type of suitcase that includes a case main body (also referred to as a case body), wheels, a handle and a force sensor. The case main body can receive the goods. The wheels are installed to a lower portion of the case main body, and one of the wheels, which is placed at a front side of the main body, serves as a driving wheel that is driven by an electric motor. The handle is installed to an upper portion of the case main body. The force sensor is installed to the handle. When the user pulls the handle while the wheels are in contact with a ground, a force, which is applied from a hand of the user to the handle, is sensed with the force sensor. The electric motor is driven based on a value of the force that is sensed with the force sensor. Therefore, the driving wheel is rotated at a speed that corresponds to the pulling force, which is applied from the user to the handle, and thereby an assist force is provided for driving the suitcase.
Furthermore, there is also known a technique of sensing a forward tilt angle of a suitcase and controlling an assist force based on the sensed forward tilt angle of the suitcase (see, for example, JP2007-125203A).
The above techniques are premised on that the suitcase is pulled by the user in the state where the suitcase is tilted forward toward the front side of the suitcase. However, besides the above-described case where the suitcase is pulled by the user, there is a case where the user is located on a side of the suitcase and runs together with the suitcase while the user is pushing the suitcase. Particularly in a case of a large suitcase, which is too large to be pulled, it is preferred to push the suitcase at the time of moving the suitcase. In such a case, an appropriate way of driving the wheels of the large suitcase needs to be provided.